Transformers are key components presently in electric power distribution networks. Generally, electric power is distributed from electrical substations at high voltage typically in excess of 6,000 volts to minimize losses. Transformers are required to reduce the voltage down to lower levels, such as 120 volts, for local distribution to commercial and residential customers
A transformer commonly used for this purpose is housed in a steel cabinet on a concrete platform or pad at ground level. The transformer itself includes primary and secondary coils housed in an oil-filled transformer well, the oil being provided to keep the coils cool. Typically, studs, to which cables, or in a general term, conductors, carrying high voltage power to the primary coils, and to which cables carrying reduced voltage from the secondary coils can be attached, protrude laterally outward from the transformer through the wall of the transformer well.
The studs are insulated from the wall of the transformer well by an insulating bushing or seal, which must be impermeable to the oil filling the transformer well. There are usually two to six studs for attaching incoming cables to the primary side, and three to four studs for attaching outgoing cables to the secondary side. Typically, there are a minimum of three studs required on the secondary side, one for each of two phases and one for a return or ground cable.
Transformers of this type may be used to deliver electric power to a relatively small number of end consumers. To supply each such consumer, one cable from each of the studs on the secondary side of the transformer is required. Typically, then, a number of cables are connected to each of the studs, one for each of the consumers being served.
Transformer connectors are used to attach the individual cables to the studs.
One of the most commonly used transformer connectors is spade connector. A spade connector has a female connection end which is screwed onto a transformer stud through the screw threads on both of the stud and the spade connector. Each cable end encapsulated in a cable end lug is screwed onto the spade connector by a set of screw through one of the cable adapting ports of the spade connector.
With these traditional spade connectors, when a transformer needs to be replaced because it is no longer functioning, an electrician has to disconnect each of the cables, usually from three to thirty cables, before the spade connector can be taken off from the stud by rotating the spade connector around the stud. Moreover, each disconnected cable has to be grounded immediately for safety reasons. After the old transformer is replaced by a new transformer and the spade connectors are connected onto the studs of the new transformer, each one of the disconnected cables then has to be bolted onto the spade connector again.
Furthermore, the cable end lug closest to the stud on the spade connector are relatively difficult to access. To reach a set of bolt and nut for a cable end lug axially closest to the stud along the cable, the electrician must reach in toward the stud over a number of cables. Even worse, the inner set bolts may not be readily visible, forcing the electrician to work blindly. Moreover, as the three or four studs are often arranged one above the other on the wall of the transformer well, the electrician may often be required to reach between two layers of cables to adjust the blot of a cable attached close to a stud. Still further, bolts might have become corroded causing extreme difficulty in removing the cables.
It is apparent that this is a lengthy and labour intensive process. It usually takes from about two and half hours to about three hours to change a transformer that carries thirty electrical cables, mainly because the time required for disconnecting and connecting the cables to the spades.
Attempts have been made to address these problems. One such attempt is multi-tap stud connectors. A multi-tap stud connector has a block structure with a transformer stud port and a plurality of cable ports. A multi-tap stud connector is connected to a transformer stud through the transformer stud port and fastened by screws along the side of the transformer stud port. To disconnect the multi-tap stud connector, one loosens the screws, typically two, and detaches the multi-tap stud connector from the transformer stud without disconnecting electrical cables. The multi-tap stud connectors are currently used as an after market product, to replace spade connectors during replacement of a non-functioning transformer. Multi-tap stud connectors have certain disadvantages. As described above, a multi-tap stud connector is connected to a transformer stud through the transformer stud port and fastened by two screws along the side of the transformer stud port. Such a connection is not as secure as the connection of a traditional spade connector, which is directly bolted on to the transformer stud. Furthermore, multi-tap connectors are made of aluminum, which is different from the transformer stud material of brass. For a long term use, the connection between aluminum and brass tends to become loose, causing poor connection between the transformer and the connector. For most transformers, particularly the large transformers, spade connectors are still the most commonly used in the field.
Therefore, it is apparent that there exists a continuing need to provide improved transformer connectors that enable the rapid change of a transformer and reduce power supply downtime. The present invention represents a novel approach toward a solution of the problems associated with the lengthy and labor intensive process involved in changing transformers.